Thank you for letting me know about signature rules, I hadn't seen any as I was uploading the image and was unaware of the helpful post that you linked. I modified my signature to the suggested 100 x 441 dimensions and compressed it to 48,73 Ko to meet the size requirement. However, when I uploaded my new signature, I noticed that the quality of the display on MMO's forums is still significantly degraded, and the size displays as 90 x 395 on my monitor.
I am curious if this is because the image is somehow still not meeting signature requirements, or if the problem is simply a display issue purely on my end. Notably, I would like to ensure that the revised signature image is within the limits permitted by the forums, as it is strange to me that it should be compressed and shrunk 10 % if it is.